Key catalogs in a content centric network

ABSTRACT

One embodiment provides a system that facilitates efficient key retrieval by using key catalogs in a content centric network. During operation, the system generates, by a client computing device, a first interest for a key indicated in a signed key catalog. In response to receiving the key, the system verifies the received key by determining that a hash of the received key matches a hash of the key as indicated in the catalog based on a name for the received key. The system generates a second interest for a content object, wherein a name for the second interest includes a name prefix associated with the key as indicated in the catalog, wherein the first interest is transmitted before or concurrent with transmitting the second interest. In response to receiving the content object, the system verifies the received content object based on the key.

RELATED APPLICATION

The subject matter of this application is related to the subject matter in the following applications:

-   -   U.S. patent application Ser. No. 13/847,814, entitled         “ORDERED-ELEMENT NAMING FOR NAME-BASED PACKET FORWARDING,” by         inventor Ignacio Solis, filed 20 Mar. 2013 (hereinafter “U.S.         patent application Ser. No. 13/847,814”);     -   U.S. patent application Ser. No. 12/338,175, entitled         “CONTROLLING THE SPREAD OF INTERESTS AND CONTENT IN A CONTENT         CENTRIC NETWORK,” by inventors Van L. Jacobson and Diana K.         Smetters, filed 18 Dec. 2008 (hereinafter “U.S. patent         application Ser. No. 12/338,175”); and     -   U.S. patent application Ser. No. 14/231,515, entitled “AGGREGATE         SIGNING OF DATA IN CONTENT CENTRIC NETWORKING,” by inventors         Ersin Uzun, Marc E. Mosko, Michael F. Plass, and Glenn C. Scott,         filed 31 Mar. 2014 (hereinafter “U.S. patent application Ser.         No. 14/231,515”);         the disclosures of which are herein incorporated by reference in         their entirety.

BACKGROUND

Field

This disclosure is generally related to the secure and efficient distribution of digital content. More specifically, this disclosure is related to a system for publishing a key catalog that enumerates key information for content offered by a producer to consumers.

Related Art

The proliferation of the Internet and e-commerce continues to create a vast amount of digital content. Content-centric network (CCN) architectures have been designed to facilitate accessing and processing such digital content. A CCN includes entities, or nodes, such as network clients and consumers, forwarders (e.g., routers), and content producers, which communicate with each other by sending interest packets for various content items and receiving content object packets in return. CCN interests and content objects are identified by their unique names, which are typically hierarchically structured variable length identifiers (HSVLI). An HSVLI can include contiguous name components ordered from a most general level to a most specific level.

A CCN content object can be signed by a producer. The content object can contain information necessary to request, locate, or identify the cryptographic keys needed to verify the signature of the producer of the content object. In order to verify the signature of a received content object, a consumer must either possess prior knowledge of the keys, or retrieve the keys based on the information included in the content object. The first approach (prior key knowledge) may be infeasible, as it is unlikely that a consumer will have knowledge of all possible producers and their signing certificate or keys prior to issuing an interest. The second approach (individual key retrieval) may introduce significant overhead, e.g., verifying a public key may require traversing a certificate chain, where each node in the chain requires another interest-content exchange. Neither approach provides an efficient system for obtaining the relevant keys for content published by a producer.

SUMMARY

One embodiment provides a system that facilitates efficient key retrieval by using key catalogs in a content centric network. During operation, the system generates, by a client computing device, a first interest for a key indicated in a signed key catalog. In response to receiving the key, the system verifies the received key by determining that a hash of the received key matches a hash of the key as indicated in the catalog based on a name for the received key. The system generates a second interest for a content object, wherein a name for the second interest includes a name prefix associated with the key as indicated in the catalog, wherein the first interest is transmitted before or concurrent with transmitting the second interest. In response to receiving the content object, the system verifies the received content object based on the key.

In some embodiments, the system generates an initial interest for the signed key catalog, wherein the catalog is digitally signed with a private key of a content producing device of the catalog. In response to receiving the signed key catalog, the system verifies the signature based on a public key of the content producing device of the catalog.

In some embodiments, the catalog is a content object with a name that is a hierarchically structured variable length identifier which comprises contiguous name components ordered from a most general level to a most specific level.

In some embodiments, the catalog indicates a collection of key sets, wherein a key set indicates one or more keys based on a name prefix associated with a respective key, a name for the respective key, and a hash of the respective key.

In some embodiments, a name for the first interest includes a name for the first key as indicated in the catalog, and the first interest indicates a hash restriction equal to a hash of the first key as indicated in the catalog.

In some embodiments, the system stores the received key in a data structure based on the name for the received key and a name prefix associated with the received key as indicated in the catalog.

In some embodiments, the system verifies the received content object by obtaining the key from a data structure. The system looks up in the catalog the name prefix included in the second interest to obtain the name of a corresponding key, and the system also looks up in the data structure the name of the corresponding key to obtain the corresponding key.

In some embodiments, the system stores, for each of one or more keys indicated in the catalog, in a data structure a mapping between a name prefix associated with a respective key, a name for the respective key, and a hash of the respective key.

In some embodiments, the system verifies the received content object by obtaining the key from a data structure. The system looks up in the data structure the name prefix included in the second interest and the name of the corresponding key to obtain the corresponding key.

In another embodiment, the system creates, by a content producing device, a key catalog that indicates a collection of key sets, wherein a key set indicates one or more keys based on a name prefix associated with a respective key, a name for the respective key, and a hash of the respective key. The system produces a digital signature for the key catalog based on a private key of the content producing device of the catalog, thereby facilitating efficient key retrieval by a client computing device.

In a variation on this embodiment, in response to receiving an interest for the digitally signed key catalog, the system transmits the catalog to a client computing device.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an exemplary network that facilitates efficient key retrieval in a CCN, in accordance with an embodiment of the present invention.

FIG. 2A presents a table depicting a format of a key catalog, in accordance with an embodiment of the present invention.

FIG. 2B presents a table depicting a format of a key catalog, in accordance with an embodiment of the present invention.

FIG. 2C presents a table depicting a format of a key catalog, in accordance with an embodiment of the present invention.

FIG. 2D presents an exemplary key catalog, in accordance with an embodiment of the present invention.

FIG. 2E presents a data structure that stores keys and other corresponding information, in accordance with an embodiment of the present invention.

FIG. 3 presents a flow chart illustrating a method by a client computing device for retrieving and using keys indicated in a key catalog, in accordance with an embodiment of the present invention.

FIG. 4 presents a flow chart illustrating a method by a client computing device for processing a key catalog by retrieving all keys indicated in the key catalog, in accordance with an embodiment of the present invention.

FIG. 5 presents a flow chart illustrating a method by a content producing device for creating a key catalog that facilitates efficient key retrieval in a CCN, in accordance with an embodiment of the present invention.

FIG. 6 illustrates an exemplary apparatus that facilitates efficient key retrieval in a CCN, in accordance with an embodiment of the present invention.

FIG. 7 illustrates an exemplary computer and communication system that facilitates efficient key retrieval in a CCN, in accordance with an embodiment of the present invention.

In the figures, like reference numerals refer to the same figure elements.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled in the art to make and use the embodiments, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

Overview

Embodiments of the present invention solve the problem of efficient key retrieval in a CCN by providing a system that allows a producer to publish a key catalog that indicates the key information for content offered by the producer to consumers. The key information in the key catalog allows a consumer to obtain a key for a corresponding name prefix either before or in parallel with requesting content under the name prefix. This removes the delay introduced by an extra (and sequential) interest for the verification key after the content is returned. The key catalog can be a single, signed CCN content object, such as a manifest, which contains one or more arbitrary key sets owned or trusted by the producer. CCN manifests are described in U.S. patent application Ser. No. 14/231,515, which disclosure is herein incorporated by reference in its entirety. A key set is an ordered and named collection of one or more key tuples, and a key tuple identifies a key based on the name prefix associated with the key, the name for the key, and the hash of the key (e.g., “(name prefix, key name, key hash)”).

Upon receiving and verifying the key catalog, a consumer can send one interest for content corresponding to a name prefix indicated in the catalog, and can also send (either before or concurrently with the interest for content) another interest for the key corresponding to that name prefix based on information from the relevant tuple. For example, if the relevant tuple is “(p1, n1, h1),” a consumer can issue an interest for a file under the “p1” namespace (e.g., “/p1/file”), and, either concurrently with or in advance of sending that interest, issue another interest for the key with the name “n1” and a hash of “h1.” When the consumer receives the requested content, the consumer may already possess the key needed to verify the requested content. Thus, by providing the consumer with an efficient mechanism to retrieve the corresponding key (e.g., either in advance or concurrent with the content retrieval), the system removes the need for an additional and sequential interest and content object exchange for the key.

The key catalog indicates key sets which indicate key tuples (as depicted below in relation to FIGS. 2A-2D. A tuple within a key set is individually addressable by its index within the collection. A key set may be embedded within the catalog or linked via their name and key ID or content object hash. Similar, a tuple may be embedded within a key set, and an individual key may be embedded within a tuple. Thus, upon receiving and verifying the key catalog, a consumer can recursively resolve all key tuples linked to from the key catalog and subsequently issue an interest for each corresponding key (as described below in relation to FIG. 2D). The consumer can store these keys in a key buffer for later use. For example, for the tuple of “(p2, n2, and h2),” if the consumer has previously requested, received, and stored the key corresponding to the namespace “p2” (e.g., the content object with the name “n2” and a content object hash of “h2”), the consumer can simply send out an interest for content corresponding to the name prefix “p2” (e.g., “/p2/file”). Upon receiving the responsive content object with the name “/p2/file,” the consumer can look up in the key buffer the corresponding key (e.g., corresponding to “n2”) and subsequently verify the content object signature on the responsive content object based on the previously stored key.

In CCN, each piece of content is individually named, and each piece of data is bound to a unique name that distinguishes the data from any other piece of data, such as other versions of the same data or data from other sources. This unique name allows a network device to request the data by disseminating a request or an interest that indicates the unique name, and can obtain the data independent from the data's storage location, network location, application, and means of transportation. The following terms are used to describe the CCN architecture:

Content Object (or “content object”): A single piece of named data, which is bound to a unique name. Content Objects are “persistent,” which means that a Content Object can move around within a computing device, or across different computing devices, but does not change. If any component of the Content Object changes, the entity that made the change creates a new Content Object that includes the updated content, and binds the new Content Object to a new unique name.

Unique Names: A name in a CCN is typically location independent and uniquely identifies a Content Object. A data-forwarding device can use the name or name prefix to forward a packet toward a network node that generates or stores the Content Object, regardless of a network address or physical location for the Content Object. In some embodiments, the name may be a hierarchically structured variable-length identifier (HSVLI). The HSVLI can be divided into several hierarchical components, which can be structured in various ways. For example, the individual name components parc, home, ccn, and test.txt can be structured in a left-oriented prefix-major fashion to form the name “/parc/home/ccn/test.txt.” Thus, the name “/parc/home/ccn” can be a “parent” or “prefix” of “/parc/home/ccn/test.txt.” Additional components can be used to distinguish between different versions of the content item, such as a collaborative document.

In some embodiments, the name can include a non-hierarchical identifier, such as a hash value that is derived from the Content Object's data (e.g., a checksum value) and/or from elements of the Content Object's name. A description of a hash-based name is described in U.S. patent application Ser. No. 13/847,814. A name can also be a flat label. Hereinafter, “name” is used to refer to any name for a piece of data in a name-data network, such as a hierarchical name or name prefix, a flat name, a fixed-length name, an arbitrary-length name, or a label (e.g., a Multiprotocol Label Switching (MPLS) label).

Interest (or “interest”): A packet that indicates a request for a piece of data, and includes a name (or a name prefix) for the piece of data. A data consumer can disseminate a request or Interest across an information-centric network, which CCN routers can propagate toward a storage device (e.g., a cache server) or a data producer that can provide the requested data to satisfy the request or Interest.

The methods disclosed herein are not limited to CCN networks and are applicable to other architectures as well. A description of a CCN architecture is described in U.S. patent application Ser. No. 12/338,175.

Exemplary Network and Environment

FIG. 1 illustrates an exemplary network that facilitates efficient key retrieval in a CCN, in accordance with an embodiment of the present invention. Network 100 can include a content requesting device 116, content producing devices 118 and 120, and a router or other forwarding device at nodes 102, 104, 106, 108, 110, 112, and 114. A node can be a computer system, an end-point representing users, and/or a device that can generate interests or originate content. A node can also be an edge router (e.g., CCN nodes 102, 104, 112, and 114) or a core router (e.g., intermediate CCN routers 106, 108, and 110). During operation, client computing device 116 can generate and send an interest 130 with a name 130.1 of “/key_catalog.” Interest 130 can travel through a network (such as a CCN) via nodes or routers 102, 110, and 112, finally reaching content producing device or producer 118. Producer 118 can generate and transmit a responsive content object 140 with a name 140.1 of “/key_catalog” and include a payload 140.2 and a signature 140.3. Payload 140.2 can correspond to a key catalog 180, which can be a table where each entry includes a key set 142 and a list of tuples 144. For example: a KeySetA 142.1 can include the tuple “(prefix1, name1, hash1)”; a KeySetB 142.2 can include the tuple “(prefix2, name2, hash2)”; and a KeySetC can include the list of tuples “(prefix3, name3, hash3), (prefix4, name4, hash4), and (prefix5, name5, and hash5).” Content object 140 can travel back to device 116, via the reverse path as interest 130 (e.g., to nodes 112, 110, and 102 before reaching device 116.

Upon receiving content object 140 (e.g., key catalog 190), device 116 may either obtain all corresponding keys based on the catalog, store the keys in a key buffer, and then issue interests for content corresponding to the name prefixes in the catalog, or, concurrently send out an interest for content corresponding to a name prefix and an interest for the corresponding key. For example, device 116 can obtain a key based on KeySetA 142.1 of key catalog 190 by issuing an interest 150 which has a name of 150.1 that includes the name of the key (“name1”) and a content object hash (“COH”) restriction with a value equal to “hash1.” The COH can also be included in a field other than the name. Interest 150 can travel through the network (e.g., via nodes 102, 108, and 114) before reaching device 120, which can return the responsive content object or key 160 to device 116. Note that either the producer of key catalog 190 (e.g., device 118) or any other device (e.g., device 120) may be the producer which returns the actual key. Device 116 can store content object or key 160 in a data structure such as a key buffer, which can indicate the name prefix, key name, and the hash of the key. The key buffer can be created based on the catalog only, e.g., prior to obtaining the actual key.

Subsequent to or concurrent with issuing interest 150, device 116 can issue an interest 170 with the name “/prefix1/file1” and receive a responsive content object 180. The name prefix for this interest (e.g., “/prefix1”) corresponds to the tuple indicated by KeySetA 142.1 in key catalog 190. Content object 180 can include a signature of producer 120. Device 116 can verify the signature on content object 180 by using the corresponding key 160 from the key buffer.

Thus, the key catalog enables a consumer to obtain the appropriate key either before or in parallel with requesting content objects under a specific namespace. This creates a more efficient system by eliminating any time required to send an additional and sequential interest for the verification key after the content is received.

Exemplary Format of a Key Catalog and a Key Buffer

FIG. 2A presents a table depicting a format of a key catalog 200, in accordance with an embodiment of the present invention. Catalog 200 is illustrated in Augmented Backus-Naur Form (ABNF) notation and can include a KeyCatalog 202 field which is a list of KeySetLinks. A KeySetLink 204 can include information to identify a “CCNx link” and a KeySet. A KeySet 206 can include a list of KeyTuples, and a KeyTuple 208 can include a KeyTupleIndex and a KeyTupleValue. A KeyTupleIndex 210 can be a number such as an OCTET, while a KeyTupleValue 212 can include the CCNx name prefix, the CCNx name of the key, and a HASH. A HASH 214 can be a number such as a 32(OCTET).

FIG. 2B presents a table depicting a format of a key catalog 220, in accordance with an embodiment of the present invention. Catalog 220 can include a name 228 which is the “CCNx Name of Key Catalog” along with 3 KeySetLinks: a KeySetLinkA 230 which includes the KeyTuple 230.4; a KeySetLinkB 240 which includes a link to the KeyTuple 240.4; and a KeySetLinkC 250 which includes a link to three KeyTuples 251.4, 252.4, and 253.4.

FIG. 2C presents a table depicting a format of a key catalog 222, in accordance with an embodiment of the present invention. Catalog 222 can include a name 228 with a value of “/parc/keys” and three KeySetLinks which correspond to KeySetLinkA 230, KeySetLinkB 240, and KeySetLinkC 250 of FIG. 2B. KeySetLinkA 230 can include a tuple identified by “(Prefix 230.1, Key Name 230.2, Hash 230.3)”; KeySetLinkB 240 can include a link to a tuple identified by “(Prefix 240.1, Key Name 240.2, Hash 240.3)”; and KeySetLinkC 250 can include a link to three tuples, “(Prefix 251.1, Key Name 251.2, Hash 251.3), (Prefix 252.1, Key Name 252.2, Hash 252.3), and (Prefix 253.1, Key Name 253.2, Hash 253.3).”

FIG. 2D presents an exemplary key catalog 224, in accordance with an embodiment of the present invention. Catalog 224 can include a name 228 with a value of “/parc/keys” and three KeySetLinks which correspond to KeySetLinkA 230, KeySetLinkB 240, and KeySetLinkC 250 of FIG. 2C. KeySetLinkA 230 can include a tuple with a value of “(/parc/p1, name1, hash1)”; KeySetLinkB 240 can include a link to a tuple with a value of “(/parc/p2, name2, hash2)”; and KeySetLinkC 250 can include a link to three tuples with respective values of “(/parc/p3, name3, hash3), (/parc/p4, name4, hash4), and (/parc/p5, name5, hash5).” A consumer in possession of catalog 224 can recursively resolve all key tuples linked to from catalog 224 and then issue an interest for each corresponding key. For example, in catalog 224, the tuple for KeySetLinkA 230 is linked and not embedded in the key set. A consumer can issue an interest 260 with a name of “/name1” and a COH of “hash1” and receive a responsive content object 262. The consumer can store content object 262 (e.g., key 262) in a key buffer. In addition, KeySetB 240 of catalog 224 is a link to a chunked key stream, i.e., a series of named content object keys that are partitioned based on a chunking protocol. The consumer can issue an interest 270.1 with a name of “/name2,” a COH of “hash2,” and a first chunk segment equal to “0,” which returns a responsive content object 272.1 or key 272.1 The consumer can then issue interests for the remaining chunks. For example, the consumer can issue an interest 270.2 with a name of “/name2,” a COH of “hash2,” and a second chunk number equal to “1,” which returns a responsive content object 272.2 or key 272.2. The chunked content object keys (e.g., keys 272.1 and 272.2) can be stored in the key buffer. Furthermore, KeySetLinkC 250 is a link to three key tuples, where the first two key tuples are linked by name and keyID or hash, and the third key is embedded within the set. The consumer can issue an interest 281 with a name of “/name3” and a COH of “hash3” and receive a responsive content object or key 291. The consumer can also issue an interest 282 with a name of “/name4” and a COH of “hash4” and receive responsive content object or key 292. Note that content object or key 293 is embedded within the key set, so the consumer does not need to issue an interest to retrieve it. The consumer can store content objects or keys 291, 292, and 293 in the key buffer. In this manner, the consumer can recursively resolve all key tuples indicated in the key catalog, and store the corresponding keys for later use.

FIG. 2E presents a data structure or key buffer 226 that stores keys and other corresponding information, in accordance with an embodiment of the present invention. Key buffer 226 can be a table where each entry includes a key name 294 and a corresponding key content object 296. For example, one entry in key buffer 226 can include a key name of “name1” and the corresponding key content object with a name of “name1” and a COH value of “hash1.” Key buffer 226 can also store the name prefix information associated with the key (not shown in FIG. 2E). Alternatively, the information from the indicated tuples in the key catalog can be stored in another data structure that is separate from the key buffer.

Client Computing Device Retrieves and Uses Keys Indicated in Key Catalog

FIG. 3 presents a flow chart 300 illustrating a method by a client computing device for retrieving and using keys indicated in a key catalog, in accordance with an embodiment of the present invention. During operation, a client computing device obtains and verifies a secure key catalog (operation 302). The key catalog can be signed by the producer of the catalog based on a private key of the producer, and the client device can verify the signature based on a public key of the producer. Next, the client device can generate two interests based on a specific name prefix from the key catalog: a first interest for a specific key; and a second interest for content. The client device can send out the first interest for the key (operation 304) either before or at the same time that the client device sends out the second interest for the content object (operation 322). By obtaining the key before or in parallel with obtaining the content, the client device can avoid the delay required for an extra and sequential interest for the key after the content is returned.

The client device can generate a first interest for a content object that corresponds to a key indicated in the key catalog based on a name for the key (operation 304). The client device can receive the responsive key content object (operation 306) and verify the key content object by looking up in the catalog the name of the key content object to obtain the corresponding hash of the key content object (operation 308). The catalog can be stored in a data structure that is the same as or separate from the key buffer which is used to store the actual keys. The client device performs a hash on the received key content object (operation 310) and determines whether the result matches the obtained hash (from the lookup in operation 308). If the result does not match, the client device drops the packet corresponding to the key content object (operation 314). If the result does match, the client device stores the key content object in the key buffer (operation 316). The client device determines if there are any more keys retrieve, as indicated in the catalog (operation 318). If there are more keys to retrieve, the client devices generates another interest for the corresponding key based on the name prefix, and the operation continues as described at operation 304. If there are no more keys to retrieve, the operation returns.

The client device can generate a second interest for content based on a name prefix indicated in the key catalog (e.g., a second content object), where the second interest has a name that includes that name prefix (operation 322). The client device can receive the responsive second content object (operation 324) and lookup in the catalog (or other data structure representing the catalog) the name prefix of the second content object to obtain the name of the corresponding key content object (operation 326). The client device can also look up in the key buffer the name of the key content object to obtain the corresponding key content object (operation 328). In some embodiments, the catalog contents (e.g., the association between the name prefix, the key name, and the key hash) are stored in the key buffer along with the actual key content object.

If the key is found in the buffer (decision 330), the client device uses the key to verify the second content object (operation 332) and the operation returns. If the key is not found in the buffer (implying that the client device has not yet obtained the corresponding key, as shown in operations 304, 306, 308, 310, 312, and 316) (decision 330), the client device can execute those operations and proceed with operation 326 (as shown by the dotted line from operation 316 to operation 326). Decision 330 can also occur before operations 322 or between any of operations 322, 324, 326, and 328. In other words, obtaining the corresponding key can occur either before or in parallel with obtaining the content for a particular namespace.

Client Computing Device Processes Key Catalog

FIG. 4 presents a flow chart 400 illustrating a method by a client computing device for processing a key catalog by retrieving all keys indicated in the key catalog, in accordance with an embodiment of the present invention. During operation, a client computing device obtains a key catalog which indicates one or more key sets, wherein a key set is an ordered and named collection of one or more key tuples, wherein a key tuple identifies a key based on a name prefix associated with the respective key, a name for the key, and a hash of the key, and wherein a key set can be embedded in the catalog or indicated as a link (operation 402). The client device performs a recursive link resolution to obtain all key sets that are indicated as a link in the key catalog (operation 403 and as described in relation to FIG. 2D). The client device generates an interest for a content object that is a key indicated in the key catalog, wherein the name for the interest includes a name for the key as indicated in the key catalog (operation 404). The interest also includes a hash restriction equal to a hash of the key as indicated in the catalog. The client device receives the responsive content object that is a key (“key content object”) (operation 406). The client device verifies the received key content object by looking up in the catalog or other data structure the name of the key content object to obtain the corresponding hash of the key content object (operation 408). The client device verifies the key content object by performing a hash on the received key content object (operation 410), and subsequently determines whether the result of the hash matched the obtained hash from operation 408 (decision 412). If the result does not match, the client device drops the corresponding packet (operation 414). If the result does match, the client device stores the received key content object in a key buffer based on the name for the key content object (operation 416).

The client device determines if there are any more keys retrieve, as indicated in the catalog (operation 418). The client device can track or mark whether a key indicated in the catalog has been retrieved and/or stored. If there are more keys to retrieve, the client devices generates another interest for the corresponding key based on the name prefix, and the operation continues as described at operation 404. If there are no more keys to retrieve, the operation returns.

Content Producing Device Creates Key Catalog

FIG. 5 presents a flow chart 500 illustrating a method by a content producing device for creating a key catalog that facilitates efficient key retrieval in a CCN, in accordance with an embodiment of the present invention. During operation, a content producing device creates a key catalog which indicates one or more key sets, wherein a key set is an ordered and named collection of one or more key tuples, wherein a key tuple is identified by a name prefix associated with the respective key, a name for the key, and a hash of the key (operation 502). A key set can be embedded in the catalog or indicated as a link. The content producing device produces a digital signature for the key catalog based on a private key of the content producing device of the catalog (operation 504). In response to receiving an interest for the digitally signed key catalog, the content producing device transmits the catalog to a client computing device (operation 506).

Exemplary Apparatus and Computer System

FIG. 6 illustrates an exemplary apparatus 600 that facilitates explicit content deletion commands, in accordance with an embodiment of the present invention. Apparatus 600 can comprise a plurality of modules which may communicate with one another via a wired or wireless communication channel. Apparatus 600 may be realized using one or more integrated circuits, and may include fewer or more modules than those shown in FIG. 6. Further, apparatus 600 may be integrated in a computer system, or realized as a separate device which is capable of communicating with other computer systems and/or devices. Specifically, apparatus 600 can comprise a communication module 602, a packet-generating module 604, a packet-verifying module 606, a catalog-managing module 608, and a content-storing module 610.

In some embodiments, communication module 602 can send and/or receive data packets to/from other network nodes across a computer network, such as a content centric network. A data packet can include an interest packet or a content object packet with a name. A data packet can also include a digitally signed key catalog or a key indicated in the key catalog. Packet-generating module 604 can generate a first interest for a key indicated in a signed key catalog. Packet-verifying module 606 can, in response to receiving the key, verify the received key by determining that a hash of the received key matches a hash of the key as indicated in the catalog based on a name for the received key. Packet-generating module 604 can generate a second interest for a content object, wherein a name for the second interest includes a name prefix associated with the key as indicated in the catalog, wherein the first interest is transmitted before or concurrent with transmitting the second interest. Packet-verifying module 606 can, in response to receiving the content object, verify the received content object based on the key.

Packet-generating module 604 can generate an initial interest for the signed key catalog, which is signed with a private key of a content producing device of the catalog. Packet-verifying module 606 can, in response to receiving the signed key catalog, verify the signature based on a public key of the content producing device of the catalog.

Content-storing module 610 can store the received key in a data structure based on the name for the received key and a name prefix associated with the received key as indicated in the catalog. Catalog-managing module 608 can look up in the catalog the name prefix included in the second interest to obtain the name of a corresponding key, and can look up in the data structure the name of the corresponding key to obtain the corresponding key. Catalog-managing module 608 can look up in the data structure the name prefix included in the second interest and the name of the corresponding key to obtain the corresponding key.

Catalog-managing module 608 can also create a key catalog that indicates a collection of key sets, wherein a key set indicates one or more keys based on a name prefix associated with a respective key, a name for the respective key, and a hash of the respective key. Catalog-managing module 608 can also produce a digital signature for the key catalog based on a private key of a content producing device of the catalog. Communication module 602 can, in response to receiving an interest for the digitally signed key catalog, transmit the catalog to a client computing device.

FIG. 7 illustrates an exemplary computer and communication system that facilitates explicit content deletion commands, in accordance with an embodiment of the present invention. Computer and communication system 702 includes a processor 704, a memory 706, and a storage device 708. Memory 706 can include a volatile memory (e.g., RAM) that serves as a managed memory, and can be used to store one or more memory pools. Furthermore, computer and communication system 702 can be coupled to a display device 710, a keyboard 712, and a pointing device 714. Storage device 708 can store an operating system 716, a content-processing system 718, and data 730.

Content-processing system 718 can include instructions, which when executed by computer and communication system 702, can cause computer and communication system 702 to perform methods and/or processes described in this disclosure. Specifically, content-processing system 718 may include instructions for generating a first interest for a key indicated in a signed key catalog (packet-generating module 722). Content-processing system 718 can include instructions for, in response to receiving the key (communication module 720), verifying the received key by determining that a hash of the received key matches a hash of the key as indicated in the catalog based on a name for the received key (packet-verifying module 724). Content-processing system 718 can include instructions for generating a second interest for a content object, wherein a name for the second interest includes a name prefix associated with the key as indicated in the catalog, wherein the first interest is transmitted before or concurrent with transmitting the second interest (packet-generating module 722). Content-processing system 718 can include instructions for, in response to receiving the content object (communication module 720), verifying the received content object based on the key (packet-verifying module 724).

Content-processing system 718 can further include instructions for generating an initial interest for the signed key catalog, which is signed with a private key of a content producing device of the catalog (packet-generating module 722). Content-processing system 718 can include instructions for, in response to receiving the signed key catalog (communication module 720), verifying the signature based on a public key of the content producing device of the catalog (packet-verifying module 724).

Content-processing system 718 can further include instructions for storing the received key in a data structure based on the name for the received key and a name prefix associated with the received key as indicated in the catalog (content-storing module 728). Content-processing system 718 can include instructions for looking up in the catalog the name prefix included in the second interest to obtain the name of a corresponding key, and looking up in the data structure the name of the corresponding key to obtain the corresponding key (catalog-managing module 726). Content-processing system 718 can also include instructions for looking up in the data structure the name prefix included in the second interest and the name of the corresponding key to obtain the corresponding key (catalog-managing module 726).

Content-processing system 718 can additionally include instructions for creating a key catalog that indicates a collection of key sets, wherein a key set indicates one or more keys based on a name prefix associated with a respective key, a name for the respective key, and a hash of the respective key (catalog-managing module 726). Content-processing system 718 can include instructions for producing a digital signature for the key catalog based on a private key of a content producing device of the catalog (catalog-managing module 726). Content-processing system 718 can include instructions for, in response to receiving an interest for the digitally signed key catalog, transmitting the catalog to a client computing device (communication module 720).

Data 730 can include any data that is required as input or that is generated as output by the methods and/or processes described in this disclosure. Specifically, data 730 can store at least: a packet that corresponds to an interest or a content object; an interest for a key; an interest for content; a key; a digital certificate; a signed key catalog; one or more key sets, where a key set indicates one or more key tuples, where a key tuple indicates a respective key based on a name prefix associated with the respective key, a name for the respective key, and a hash of the respective key; a name prefix; a name for a key; a hierarchically structured variable length identifier; a hash of a key; a data structure; a data structure that can store a mapping between a name prefix, a key name, and a key hash; and a data structure or buffer that can store a mapping between a name prefix and a key name, and a content object that is a key.

The data structures and code described in this detailed description are typically stored on a computer-readable storage medium, which may be any device or medium that can store code and/or data for use by a computer system. The computer-readable storage medium includes, but is not limited to, volatile memory, non-volatile memory, magnetic and optical storage devices such as disk drives, magnetic tape, CDs (compact discs), DVDs (digital versatile discs or digital video discs), or other media capable of storing computer-readable media now known or later developed.

The methods and processes described in the detailed description section can be embodied as code and/or data, which can be stored in a computer-readable storage medium as described above. When a computer system reads and executes the code and/or data stored on the computer-readable storage medium, the computer system performs the methods and processes embodied as data structures and code and stored within the computer-readable storage medium.

Furthermore, the methods and processes described above can be included in hardware modules or apparatus. The hardware modules or apparatus can include, but are not limited to, application-specific integrated circuit (ASIC) chips, field-programmable gate arrays (FPGAs), dedicated or shared processors that execute a particular software module or a piece of code at a particular time, and other programmable-logic devices now known or later developed. When the hardware modules or apparatus are activated, they perform the methods and processes included within them.

The foregoing descriptions of embodiments of the present invention have been presented for purposes of illustration and description only. They are not intended to be exhaustive or to limit the present invention to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present invention. The scope of the present invention is defined by the appended claims. 

What is claimed is:
 1. A computer system to facilitate key retrieval, comprising: a processor; a storage device coupled to the processor and storing instructions that when executed by a computer cause the computer to perform a method, the method comprising: generating, by a client computing device, a first interest for a key indicated in a signed key catalog, wherein the key indicated in the signed key catalog is embedded within a key set such that a request for another key within the signed key catalog functions as the first interest, wherein the signed key catalog comprises a link to a chunked key stream partitioned based on a chunking protocol; in response to receiving the key as a received key, verifying the received key by determining that a hash of the received key matches a hash of the key as indicated in the catalog based on a name for the received key; generating a second interest for a content object, wherein a name for the second interest includes a name prefix associated with the key as indicated in the catalog, wherein the first interest is transmitted before or concurrent with transmitting the second interest; and in response to receiving the content object, verifying the received content object based on the key.
 2. The computer system of claim 1, wherein the method further comprises: generating an initial interest for the signed key catalog, wherein the catalog is digitally signed with a private key of a content producing device of the catalog; and in response to receiving the signed key catalog, verifying the signature based on a public key of the content producing device of the catalog.
 3. The computer system of claim 1, wherein the catalog is a content object with a name that is a hierarchically structured variable length identifier which comprises contiguous name components ordered from a most general level to a most specific level.
 4. The computer system of claim 1, wherein the catalog indicates a collection of key sets, wherein a key set indicates one or more keys based on a name prefix associated with a respective key, a name for the respective key, and a hash of the respective key.
 5. The computer system of claim 1, wherein a name for the first interest includes a name for the first key as indicated in the catalog, and wherein the first interest indicates a hash restriction equal to a hash of the first key as indicated in the catalog.
 6. The computer system of claim 1, wherein the method further comprises: storing the received key in a data structure based on the name for the received key and a name prefix associated with the received key as indicated in the catalog.
 7. The computer system of claim 1, wherein verifying the received content object further comprises obtaining the key from a data structure, which involves: looking up in the catalog the name prefix included in the second interest to obtain the name of a corresponding key; and looking up in the data structure the name of the corresponding key to obtain the corresponding key.
 8. The computer system of claim 1, wherein the method further comprises: storing, for each of one or more keys indicated in the catalog, in a data structure a mapping between a name prefix associated with a respective key, a name for the respective key, and a hash of the respective key.
 9. The computer system of claim 8, wherein verifying the received content object further comprises obtaining the key from a data structure, which involves: looking up in the data structure the name prefix included in the second interest and the name of the corresponding key to obtain the corresponding key.
 10. A computer-implemented method to facilitate key retrieval, the method comprising: generating, by a client computing device, a first interest for a key indicated in a signed key catalog, wherein the key indicated in the signed key catalog is embedded within a key set such that a request for another key within the signed key catalog functions as the first interest, wherein the signed key catalog comprises a link to a chunked key stream partitioned based on a chunking protocol; in response to receiving the key as a received key, verifying the received key by determining that a hash of the received key matches a hash of the key as indicated in the catalog based on a name for the received key; generating a second interest for a content object, wherein a name for the second interest includes a name prefix associated with the key as indicated in the catalog, wherein the first interest is transmitted before or concurrent with transmitting the second interest; and in response to receiving the content object, verifying the received content object based on the key.
 11. The method of claim 10, further comprising: generating an initial interest for the signed key catalog, wherein the catalog is digitally signed with a private key of a content producing device of the catalog; and in response to receiving the signed key catalog, verifying the signature based on a public key of the content producing device of the catalog.
 12. The method of claim 10, wherein the catalog is a content object with a name that is a hierarchically structured variable length identifier which comprises contiguous name components ordered from a most general level to a most specific level.
 13. The method of claim 10, wherein the catalog indicates a collection of key sets, wherein a key set indicates one or more keys based on a name prefix associated with a respective key, a name for the respective key, and a hash of the respective key.
 14. The method of claim 10, wherein a name for the first interest includes a name for the first key as indicated in the catalog, and wherein the first interest indicates a hash restriction equal to a hash of the first key as indicated in the catalog.
 15. The method of claim 10, further comprising: storing the received key in a data structure based on the name for the received key and a name prefix associated with the received key as indicated in the catalog.
 16. The method of claim 10, wherein verifying the received content object further comprises obtaining the key from a data structure, which involves: looking up in the catalog the name prefix included in the second interest to obtain the name of a corresponding key; and looking up in the data structure the name of the corresponding key to obtain the corresponding key.
 17. The method of claim 10, further comprising: storing, for each of one or more keys indicated in the catalog, in a data structure a mapping between a name prefix associated with a respective key, a name for the respective key, and a hash of the respective key.
 18. The method of claim 17, wherein verifying the received content object further comprises obtaining the key from a data structure, which involves: looking up in the data structure the name prefix included in the second interest and the name of the corresponding key to obtain the corresponding key.
 19. A computer system to facilitate key retrieval, comprising: a processor; a storage device coupled to the processor and storing instructions that when executed by a computer cause the computer to perform a method, the method comprising creating, by a content producing device, a key catalog that indicates a collection of key sets, wherein a key set indicates one or more keys based on a name prefix associated with a respective key, a name for the respective key, and a hash of the respective key; and producing a digital signature for the key catalog based on a private key of the content producing device of the catalog, wherein a given key in the key catalog is embedded within a given key set such that a request for another key within the key catalog functions as a first interest in a content-centric network, and wherein the signed key catalog comprises a link to a chunked key stream partitioned based on a chunking protocol.
 20. The computer system of claim 19, wherein the method further comprises: in response to receiving an interest for the digitally signed key catalog, transmitting the catalog to a client computing device. 